Abstract
Purpose: Lifestyle risk factors are implicated in driving the current surge in myopia prevalence yet, paradoxically, known risk factors explain little of the variation in refractive error in the population. Here, we applied ‘instrumental variable’ methods designed to avoid reverse causation and reduce confounding bias, to gauge lifestyle risk factor effect sizes.
Methods: Three myopia risk factors (time outdoors, time reading, and sleep duration) were assessed in participants of the Avon Longitudinal Study of Parents and Children (ALSPAC): a cross-sectional sample of 2302 children aged 15 years old and a longitudinal sample of 3086 children followed from age 7 to 15 years. Seven instrumental variables were considered jointly: dog ownership, cat ownership, bedtime variability, birth order, and polygenic scores quantifying genetic predisposition to spend additional time outdoors, years in full time education, and time asleep overnight.
Results: Risk factor effect sizes were 4-fold to 9-fold higher in the instrumental variable analyses compared to conventional regression analyses. In instrumental variable analyses, one extra hour spent outdoors every day during childhood was associated with a shift towards hyperopia of +0.53 to +0.94 D, while one extra hour spent reading every day was associated with a shift towards myopia of -0.44 to -0.88 D. There was inconsistent evidence that sleep duration influenced refractive error.
Conclusion: Myopia risk factor effects were underestimated up to 9-fold in conventional analyses in this sample, compared to instrumental variable analyses. Translational Relevance: We speculate the effects of lifestyle risk factors for myopia have been underestimated in past studies
Methods: Three myopia risk factors (time outdoors, time reading, and sleep duration) were assessed in participants of the Avon Longitudinal Study of Parents and Children (ALSPAC): a cross-sectional sample of 2302 children aged 15 years old and a longitudinal sample of 3086 children followed from age 7 to 15 years. Seven instrumental variables were considered jointly: dog ownership, cat ownership, bedtime variability, birth order, and polygenic scores quantifying genetic predisposition to spend additional time outdoors, years in full time education, and time asleep overnight.
Results: Risk factor effect sizes were 4-fold to 9-fold higher in the instrumental variable analyses compared to conventional regression analyses. In instrumental variable analyses, one extra hour spent outdoors every day during childhood was associated with a shift towards hyperopia of +0.53 to +0.94 D, while one extra hour spent reading every day was associated with a shift towards myopia of -0.44 to -0.88 D. There was inconsistent evidence that sleep duration influenced refractive error.
Conclusion: Myopia risk factor effects were underestimated up to 9-fold in conventional analyses in this sample, compared to instrumental variable analyses. Translational Relevance: We speculate the effects of lifestyle risk factors for myopia have been underestimated in past studies
| Original language | English |
|---|---|
| Article number | 10 |
| Journal | Translational Vision Science and Technology |
| Volume | 13 |
| Issue number | 11 |
| DOIs | |
| Publication status | Published - 1 Nov 2024 |
Bibliographical note
Publisher Copyright:© 2024 The Authors.
Keywords
- ALSPAC
- educational attainment
- instrumental variable
- myopia
- sleep
- time outdoors